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Yellowstone National Park's Wolf Population Down More than 25 Percent

How healthy is Yellowstone National Park's wolf population? While wildlife biologists say the wolves overall are doing well and that the recovery program launched in 1995 has indeed succeeded, this past year was tough for the park's keystone predators.

Disease and infighting are being blamed for a drop of more than 25 percent in the numbers of wolves in Yellowstone. While the drop from 171 wolves in 2007 to 124 in 2008, or 27 percent, seems staggering, back in 2005 the numbers showed a slightly greater drop, from 171 wolves counted in 2004 to 118.

Plus, Yellowstone officials say last year's decline was the first drop in wolf numbers in the park in three years.

The greatest decline occurred on the northern range, the area with the greatest wolf population density. The wolf population there dropped 40 percent, from 94 to 56 wolves. The decline in the wolf population in the interior of the park was smaller. That population dipped from 77 to 68 animals, off 11 percent from the previous year.

The number of breeding pairs in the park also declined from 10 to six. This is the lowest number of breeding pairs recorded since 2000 when wolves first met the minimum population requirement for delisting.

Previous population declines in 1999 and 2005 were attributed to the impacts of disease, especially on wolf pups. This past year, distemper, mange, and wolves killing each other are the likely causes of the population decline.

Distemper is fairly common in wildlife and is believed to be the major contributor to the recent decline in the population of wolf pups in the park. The often fatal virus can be found in and readily transmitted between wolves and other animals such as coyotes, foxes, raccoons, and skunks.

Biologists will capture and sample wolves to confirm that distemper is indeed affecting wolves. In 1999 and 2005 distemper was found in both wolves and coyotes.

Mange is a parasitic infection of the skin. It can weaken the animal, making it susceptible to infections and other problems which can lead to death.

Finally, wolves often kill each other over competition for food or territory. Population density could contribute to an increase in wolf-on-wolf mortality.

Multi-year research projects are underway to help wildlife biologists better understand the impacts of disease and of animal social dynamics on wolf population changes.

Comments

Can't they inoculate the wolves against distemper as well as giving them rabies shots at the same time to control both diseases. This will give us a healthier population. Before anyone complains that we are messing with nature we already have that's why their populations are low in the first place. We exterminated them and then brought them back.

Of course they can't inoculate wolves against any disease. They are suppose to be wild animals. Nature will work out the survival issue. The strongest and those with a healthy immune system will survive, and their offspring will then inherit the strength of the parents. To immunize wolves would be declaring them 1) they are not a wild animal or 2) they are a non native species unable to survive without human intervention in the ecosystem to which they were transplanted.

If the population was too high to support them, then a natural reduction is better than a planned hunt. It seems the mechanism to adjust population to the terriortory by natural means is in effect.

Many animals die from distemper. If you want a wild population that means you do not vaccinate.

Vaccination in human population areas by leaving out food with rabies vaccination is done to reduce rabies in rabbits, foxes and skunks to name a few and to reduce the possibilty of contamination into pets such as cats and dogs.

Vaccinating wild animals in national parks is a controversial issue, to be sure. Wildlife biologists prefer to avoid vaccination where possible, but sometimes there's little choice, as when critically endangered populations are at imminent risk of catastrophe. One example that leaps to kind is the sylvatic plague threat to black-footed ferrets in and near Badlands National Park. Resorting to a vigorous campaign of insecticide spraying and vaccination was probably the only way to save this struggling population.

What is considered to be an optimal population density for wolves? Is that number the same as a naturally-occurring population density? Are there any reliable estimates for wolf population density before European settlement of North America?